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1989 Sedan Deville
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3 Posts
Discussion Starter · #1 ·
I am new to Cadillac ownership and bought an 89 Sedan Deville.
When I turn on the switch for the cruise control The small light comes on to the right of the switch. Then when I go to set the speed the "Engaged" Light comes on but when I take my foot off the gas, the car slows down. I have tried to use the accelerator switch on the steering column and get nothing. Any Ideas?

Problem 2

I have no heat whatsoever. The digital display works fine. I can set a temp, turn the fan on/off, turn on defrost and it blows cold air, even with temp set at 80 degrees.

When I first turn the key to the on position, I hear what sounds like a small electric motor running, then what sounds like a door with a spring closing , (with a thud noise).

Please help me, I have fallen in love with this car and would like to get it.

Here are some pics.
 

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Super Moderator
2010 DTS
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88,476 Posts
Cruise Control
Check the fuse. Look under the dash by the steering column. There should be 2 green plugs. Make sure they are connected together. Check the diaphragm under the hood and be sure it is connected to the throttle linkage.

Heat
I'd start by flushing the heater core.
 

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85 Coupe Deville 4.1 V8 & 4.3 V6 Deisel & 1970 Eldorado
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773 Posts
On the heat, You can go into the on board diagnostics. There you can compare the commanded blend door position and the actual blend door position. This confirms that the blend door servo has not failed. If this checks, Then check to make sure that the blend door actuator rod is indeed connected on both ends. (May need to remove the glove box to make seeing easier). If both of these check out, Then suspect a clogged heater core. Check the temp of the hoses and see if they are close to the same temp.

On the cruise check to make sure that there is adequate vacuum at the servo. Then make sure that the vacuum disconnect switch and hose are operating correctly. This hose runs from the servo to the brake light switch. It's purpose it to insure that the cruise control disconnects in the event an electrical failure doesn't release control of the throttle. Check for trouble codes related to the cruise. I sounds like the trouble is vacuum related.
 

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92 Deville
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548 Posts
I think the parking break and cruse control vacuum are on the same line.
Does the park break release work?
 

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1989 Sedan Deville
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3 Posts
Discussion Starter · #5 ·
Thanks Guys! On the heat, I found vacuum operated lever hooked to what looks like a check valve on the heater core feed line that had the vacuum line broke off.
I am thinking about bypassing it. could that cause a problem? I also flushed out the heater core, first through the return hose, Till the water was clear, then trough the feed line, again till water was clear. I did this twice and now I have great heat.

Next thing to tackle will be to trace the vacuum lines to the cruise control.
 
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